FREEZE DRYING CHARACTERISTICS OF MUSHROOMS

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dc.contributor.advisorEDUKONDALU, L
dc.contributor.authorBRAHMINI, B
dc.date.accessioned2018-12-29T05:09:58Z
dc.date.available2018-12-29T05:09:58Z
dc.date.issued2018
dc.descriptionD5554en_US
dc.description.abstractMushroom is a macro-fungus with a distinctive fruiting body, which can be hypogeous or epigeous, large enough to be seen with the naked eye and to be picked by hand. Mushroom has been valued throughout the world as both food and medicine for thousands of years. Button mushroom (Agaricus bisporus L.) is the most widely cultivated and consumed mushroom in the world. It contributes about 90 per cent of total country’s production as against its global share of about 40 per cent. Button mushrooms are highly perishable due to their high moisture content. Once the fruiting body matures, degradation process starts and it becomes inconsumable after some time. Due to its short shelf-life, mushroom is usually dehydrated for preservation. Drying of mushrooms by conventional methods is generally practiced to reduce water activity, but, results in nutritional losses, characteristic colour deterioration and structure deformation. To overcome these problems, freeze-drying of mushroom slices was investigated. White button mushrooms after cleaning were vertically cut into 2, 4, 6 and 8 mm thick slices. Sliced mushrooms were frozen at −20 °C and then subjected to the freeze drying at various heating plate temperatures of 10, 20, 30 and 40 °C. Weight reduction values were recorded during the drying to determine the drying characteristics such as moisture content (% d.b.), moisture ratio and drying rate (% d.b. min-1). The experimental moisture ratio data were fitted to the five thin layer drying models. Three statistical parameters, namely coefficient of determination (R2), reduced-χ2and root mean square error (RMSE), were used to test the mathematical models. Freeze dried mushroom slices were rehydrated in water at 20, 40 and 60 °C. The effect of slice thickness and heating plate temperature on physicochemical properties like bulk density, porosity, firmness, shrinkage, water activity, colour, ascorbic acid, protein, dietary fiber and microbial properties like total bacterial, yeast and mould were evaluated immediately after freeze drying and during the storage. Moisture content of the fresh slices was found to be in the range of 1547 to 1427% (d.b.) and it was reduced to less than 5.41% (d.b.) after the freeze drying at various heating plate temperatures. Freeze drying of mushroom slices took place entirely in falling rate period. Moisture content, moisture ratio and drying rate decreased continuously with an increase in the heating plate temperature and decrease in the slice thickness. All the models gave the best fitting results, however, the Page model showed lower RMSE (0.0016), reduced- χ2 (3.52x10-4) and highest R2 (1.000) value. Samples with lower thickness and dried at higher plate temperature exhibited higher rehydration ratio (RR). All the samples rehydrated at 20 °C exhibited the highest RR values. Increase in slice thickness resulted in higher bulk density (0.1524 g cm-3), firmness (8.98 N), water activity (0.311), shrinkage (5.32%), ascorbic acid (25.95 mg/100 g) and protein content (31.02%), but, lower porosity (79.85%) and rehydration ratio (2.89). The increase in heating plate temperature resulted in increase in rehydration ratio (6.3067), porosity (89.31%), firmness (8.98 N) and colour change, but, decrease in shrinkage (1.8%), bulk density (0.07 g cm-3), ascorbic acid (16.18 mg/100 g), protein (24.58%) and dietary fibre content (16.23%). No microbial growth was observed in freeze dried mushroom slices. Firmness, rehydration ratio, porosity, ascorbic acid and protein content of all the samples decreased during the storage, whereas, the water activity increased with the storage period. This may be due to the absorption of moisture during the storage. Microbial analysis indicated by yeast count, mould count and total plate count was not detectable during the first three weeks of storage, whereas in the fourth week negligible growth was observed. This may be due to the low water activity of stored samples. Keywords: Slice thickness; Plate temperature; Modeling; Rehydration; Physicochemical propertiesen_US
dc.identifier.urihttp://krishikosh.egranth.ac.in/handle/1/5810086657
dc.keywordsFREEZE DRYING, MUSHROOMSen_US
dc.language.isoen_USen_US
dc.pages112en_US
dc.publisherAcharya N.G. Ranga Agricultural Universityen_US
dc.research.problemFREEZE DRYING CHARACTERISTICS OF MUSHROOMSen_US
dc.subAgricultural Engineeringen_US
dc.subjectnullen_US
dc.themeFREEZE DRYING CHARACTERISTICS OF MUSHROOMSen_US
dc.these.typeM.Tech.en_US
dc.titleFREEZE DRYING CHARACTERISTICS OF MUSHROOMSen_US
dc.typeThesisen_US
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